Doctor going on vacation early billed UK resident (7)
I believe the answer is:
greylag
'billed uk resident' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'doctor going on vacation early' is the wordplay.
'doctor' indicates an anagram.
'on vacation' means to remove the middle letters (after the inside letters have vacated the word).
'going' with its centre removed is 'gg'.
'gg'+'early'='ggearly'
'ggearly' with letters rearranged gives 'GREYLAG'.
Can you help me to learn more?
(Other definitions for greylag that I've seen before include "Wild goose -- eg gyral (anag)" , "bird?" , "Breed of goose - Lyra egg (anag)" , "Eurasian goose" , "Large goose" .)